//
//
// This file is for Assignment 5, BU CAS CS 520, Fall, 2010
//
//

(* ****** ****** *)

dataview
slseg_v (
  a:t@ype+, int, addr, addr
) =
  | {l:addr} slseg_v_nil (a, 0, l, l) of ()
  | {l_fst,l_lst:addr | l_fst > null} {l_nxt:addr} {n:nat}
    slseg_v_cons (a, n+1, l_fst, l_lst) of 
      ((a, ptr (l_nxt)) @ l_fst, slseg_v (a, n, l_nxt, l_lst))
// end of [slseg_v]

(* ****** ****** *)

viewdef cycbuf_v (
  a:t@ype, m:int, n:int, l_fst: addr, l_lst: addr
) = (slseg_v (a, n, l_fst, l_lst), slseg_v (a?, m-n, l_lst, l_fst))

(* ****** ****** *)
//
// HX: 20 points
//
fun{a:t@ype}
cycbuf_insert_back
  {m,n:int | 0 <= n; n < m} {l_fst,l_lst:addr} (
  pf: cycbuf_v (a, m, n, l_fst, l_lst) | p_lst: ptr l_lst, x: a
) : [l_lst:addr] (cycbuf_v (a, m, n+1, l_fst, l_lst) | ptr l_lst)

(* ****** ****** *)
//
// HX: 20 points
//
fun{a:t@ype}
cycbuf_remove_frnt
  {m,n:int | 0 < n; n <= m} {l_fst,l_lst:addr} (
  pf: cycbuf_v (a, m, n, l_fst, l_lst) | p_fst: ptr l_fst, x: &a? >> a
) : [l_fst:addr] (cycbuf_v (a, m, n-1, l_fst, l_lst) | ptr l_fst)

(* ****** ****** *)

(* end of [cycbuf.sats] *)